Hurricane warnings across Caribbean islands battered by Irma continued to expand with Tropical Storm Maria expected to become a hurricane later today.

Over the next three days, National Hurricane Center forecasters say Maria will likely intensify to a hurricane as it nears the Lesser Antilles Monday and Tuesday, although slower progress may spare the islands some of the strongest winds. By mid week, Maria could near the Virgin Islands and Puerto Rico as a major hurricane, which could come under hurricane warnings as early as tonight.

In their 11 a.m. update, forecasters said Maria is expected to continue heading to the west-northwest for the next four days but should slow, bringing it close to the Leeward Islands early this week.

A hurricane hunter plane is scheduled to fly into the storm later today.

It’s too soon to tell Maria’s impacts to Florida or the U.S. coast. Early models show the storm moving toward Florida and up the east coast, but forecasts so far in advance can be hundreds of miles off.

Maria was located 450 miles east-southeast of the Leeward Islands with sustained winds of 65 mph at 11 a.m. The storm was moving west-northwest at 15 mph. Tropical storm force winds extended 60 miles from Maria’s center.

St. Martin and St. Bart’s, both pounded by Irma, were added Sunday to the list of islands now under hurricane watches. They include Antigua, Barbuda, St. Kitts, Nevis, Montserrat, Guadeloupe, Dominica, Saba, St. Eustatius, Anguilla, Barbados and St. Lucia.

At 11 a.m. Sunday, National Hurricane Center forecasters warned Maria is expected to cross the Lesser Antilles as a hurricane and near Puerto Rico as a major storm next week.

National Hurricane Center

Last week, Irma’s ferocious Category 5 winds left a wake of destruction that damaged more than 90 percent of the buildings on Barbuda and forced all its residents to flee. On St. Martin, residents are wondering if it’s even possible to rebuild.

Forecasters say Maria is facing conditions eerily similar to the path Irma took — low wind shear, a warm ocean and very moist air — and warned the storm could intensify even more than they’ve so far projected.

Maria is being steered by a high-pressure ridge to the west-northwest. That ridge is expected to weaken in the next three days, which could slow the storm but keep it headed in the same direction.

National Hurricane Center

As it nears the coast, Hurricane Jose, now about 355 miles southeast of Cape Hatteras and headed toward the New England coast, could play a factor in where Maria goes. If Jose weakens the ridge steering the storm, it could allow Maria to take a track more to the northwest or north-northwest. If not, the storm will likely keep heading to the west-northwest.

Sunday morning, Jose strengthened slightly, but forecasters say it will likely weaken in the coming days as it faces stronger wind shear, and then moves over colder water. They expect it to weaken again to a tropical storm in three to four days.

Forecasters warned the islands could again be hit with heavy storm surge, from four to six feet deep. The central and southern Leeward Islands could get between six and 12 inches of rain, with 20 inches possible in some locations. Dangerous waves and rip currents will likely pick up around the Lesser Antilles Sunday night.

Maria will become the seventh hurricane this season in what was expected to be an above average year, with five to nine hurricanes and two to five major storms predicted. But 2017 may end up easily beating that forecast with more than two months to go during the busiest part of the Atlantic season.

National Oceanic and Atmospheric Administration

Forecasters are also watching Tropical Storm Lee, located nearly 875 miles west-southwest of the Cabo Verde Islands. Lee weakened to a depression Sunday, poses no threat to land and is expected to fizzle by Tuesday.